Centrifugal switch.



G. B. HANRIGHT.

GBNTRIPUGAL SWITCH.

APPLICATION FILLED JUNE 14, 1909.

992,870, Patented May 23, 1911.

M 56 14 l l M ,i' I; v 4/ Q0 4- o \52/ M 1 5 M 5 12/ 45 /8 A6 & Ijevenlor UNITED STATES PATENT OFFICE.

CLA ENGE B. HANRIGHT, 0F CAMBRIDGE, MASSACHUSETTS, ASSIGNOR, TU TI IETZER-GABOT ELECTRIC COMPANY, OF BROOKLINE, MASSACHUSETTS, A COR-PORATION OF MASSACHUSETTS.

CENTRIFUGAL SWITCH.

Specification of Letters Patent.

Application filed June 14, 1909. Serial No. 501,892.

To all whom it may concern:

Be it known that I, CLARnNon B. HAN- RIGHT, a citizen of the UnitedStates, residing at Cambridge, in the county of Middlesex and State ofMassachusetts, have invented certain new and useful Improvements inCentrifugal Switches; and I do hereby declare the following to be afull, clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

The invention relates to centrifugal switches.

While this switch is especially'intended for use in connection withsingle-phase induction motors of the type designed to be started withauxiliary windings in parallel with a working coil, or winding whichauxiliary windings are cut out when a predetermined speed is attained,it is not limited to such" use, as it may be used for other purposeseither to open or close a circuit when the rotary element to which it isattached attains or exceeds a predetermined speed.

Circuit interrupters, to be durable and reliable in operation, must actquickly so as to prevent injurious sparking, for the slow breaking of acircuit, and especially a circuit like that above mentioned, results ina rapid deterioration of the switch contacts.

The primary object of the invention is therefore to produce 'acentrifugal switch with movable contacts, the incipient movements ofwhich, when a predetermined speed is attained, precipitate a rapidcompletion of the opening movements. It is also desirable that theswitch should not close again until the rate of speed has beenmaterially reduced, so that minor changes of speed, due to variations inload or other causes, will not produce a closing movement of the switch.

To this end the present invention contemplates the use of a contactmember-occupyingclosed or open position when at rest and at low speeds,and a weighted pivoted member arranged to actuate the former by itsmovement under the influence of cen trifugal force when thepredetermined speed is attained. The weighted member is so located withrespect to the contact member, and cooperates with it in such a mannerthat its incipient movement under the action of the centrifugal force,precipitates rapid opening (or closing) movement of the con tact member.

In the accompanying drawing Figure 1 is a plan view of the switch inclosed position showing diagrammatically the circuit connections for asingle-phase motor; Fig. 2 is a plan view of the switch in openposition; and Fig. 3 is a central vertical section through the switch. 3

As shown in the drawings, the switch comprises a plate or disk 1 whichmay be made of brass or any other suitable conducting material which isreadily cut and bent into shape by means of punches and dies. The plate1 is mounted upon a hub 2 but insulated therefrom by means of insulatingwashers 4 which are held between a shoulder formed on the hub 2 and anut 6 screwthreaded upon the hub and retained in position by a set-screw8. The hub 2 is adapted to be mounted upon a shaft 10 which is the mainshaftof the motor. Pivoted to the plate 1 are two opposed contactorbrush-carrying levers 12 and l lprovided with offset portions 15 and 16respectively upon which contact blocks or brushes 18 and 19 respectivelyare pivotally mounted. Pivotally mounted upon the disk 1 are centrifugalbrush-carrier actuating arms 20 and 22 which are provided at their outerends with a seriesof washers 24 held in place by screws 25, and adaptedto be thrown outwardly by centrifugal force when the -motor reaches apredetermined speed. By

varying the number of washers the critical speed may be varied; The arms20 and 22 are provided with inwardly ext-ended horns 28 which areadapted to engage the opposing portions 30 of the brush-carrying levers12 and 14. Coiled springs 32 and 34 are connected to the levers 12 and14 and the corresponding arms 20and 22. These springs are attached tothe levers and arms at points between their pivots and their ends whichmove outwardly; The movement of the levers 12 and 14 is limited by stops36 and 38 which project upwardly from the plate 1 into the path oftravel of said levers.

A pair of contact segments 40 and 41 are insulated from each other andmounted upon a stationary portion of the mot-or frame.

These segments are adapted to be engaged by the brushes 18 and 19 whichare pivoted to the brush levers so that they may prop- I erly contactwith said segments during their revolution about the same. Thebrush-carrier actuating arms 20 and- 22 while structurally independentof the brush-carrier levers, being separate devices, are operativelyarticulated therewith, so that while the carriers may (if desired) bebalanced in their low-speed positions they are ada ted to be actuated,not by their own centrifugal force, but by the movements of theirrespective actuating arms.

The motor circuit includes a working coil 44 which is connected directlyacross the line wires {45 and 46, and also contains a starting coil 48which is connected at one end to the wire 45 and at its other end to thesegment 40. The segment 41 is connected to the line wire 46. During thestarting of the motor the switch is in the position shown in Fig. 1 inwhich the starting coil. '48 operates in parallel with the working coil44. lDuring the rotation of the motor the brushes'18 and 19 aremaintained in contact with the segments 40 and 41 by the springs 32 and34. When the motor attains a predetermined speed, the Weighted ends ofthe arms 20 and 22 fly outwardly, andthe horns 28 deliver a blow to theopposing portions of the bell crank levers 12 and 14, so that theincipient movement of the weighted arms acts to forcibly precipitaterapid. movement of the contact brushes from the segments 40 and 41 toquickly break the circuit through the starting coil, that is to say, thearms 20 and 22 being 1n unstable equilibrium as the motor speedapproaches a certain critical maximum, the unbalanced centrifugal force,upon the attalnment of such maximum, will move the arms 20 and 22suddenly outwardly so as to cause said arms to deliver blows to the bellcrank levers 12 and 14. As the weighted arms move-outwardly, theleverage of the springs upon the arms and bell crank levers is reduced,as will be seen by reference" to Fig. 2. Thus a considerable force willbe required todrawihe weighted arms nd the contact brushes inwardlyagainst the se ments 40 and 41. This allows a considera le fluctuationin speed in the motor without causing the contact brushes to be broughtinto contact with the segments until a certain predetermined lesser orminimum speed of rotation is reached.

It is to be observed that the various parts of the switch may be formedof sheet metal, which is readily cut and punched into shape, thusafiording a construction which is durable, yet readily and cheaplymanufactured.

Having thus described the invention, what is claimed is 1. A centrifugalswitch having, in combination, a rotary support, a movable contactmember mounted upon said support, independent centrifugal actuatingmeans spring also being arranged to overcome the centrifugal force andsuddenly move said centrifugal means when a certain-predeterminedminimum speed of rotation is reached, substantially as described.

2. A centrifugal switch having, in combination, a rotary support, acontact member mounted upon the support, and independent centrifugalactuating means for moving the contact member comprising a Weightedmember and a spring so arranged that the weighted member is heldstationary by the spring until a predetermined critical speed ofrotation is attained and is then released to move suddenly and strike ahammer blow upon the contact member, substantially as described.

3. A centrifugal switch, having, in combination, a rotary support, acontact member mounted upon said support, an independent centrifugal armfor actuating the contact member and a spring acting first increasinglyand'later decreasingly to resist the actuating movement of the armduringt-he approximation of starting speed to the operating speed,substantially as described.

4. A centrifugal switch, having, in combination, a rotary support, apair of contact members mounted upon said support, and weighted armspivotally mounted upon said support, and articulated with sa1d contactmembers to actuate them when the rotary member attains a predeterminedspeed, substantially as described.

5. A centrifugal switch, having, in combination, a rotary support, apair of contact-carrying levers mounted upon said support, brushes onsaid levers, a pair of weighted arms pivotally mounted upon saidsupport, and springs connecting the levers and the arms acting to exertpulls on the levers in the direction to oppose centrifugal force,substantially as described.

6. A centrifugal switch, having, in combination, a rotary support, apair of contact-carrying levers mounted upon said support, brushespivoted to said levers, a pair of weighted arms pivotally mounted uponsaid support, springs connecting the levers and the arms acting to exertpulls on the levers in the direction to maintain the contact members inclosed position, and means for limiting the outward movement of saidarms, substantially as described.

7. A centrifugalswitch, having, in combination, a plurality of contacts,a rotary support, a pair of opposed brush carriers mounted thereon,brushes mounted on said carriers, and cooperating with said contacts,

a pair of centrifugal brush carrier actuating ariiis,'-and;. prings andweights operatively relatedto' the arms to determine the critical speedat which the brushes are to be separated from the contacts,substantially as described.

8. A centrifugal switch having, in combination, a rotary support, acontact member mounted upon said support, and independent centrifugalactuating means for moving the contact member arranged to be held inunstable equilibrium as a predetermined speed of rotation is approachedand then upon the attainment of said predetermined speed of rotation tosuddenly move under the action of centrifugal force and deliver ablowglpon the contact member, substantially as described.

9. A centrifugal switch, having, in combination, a rotary support, acontact member mounted upon said support, independent centrifugalactuating means for movlng said contact member in one direction when apredetermined speed is reached and means for moving the contact memberin the other direction when a lesser predetermined speed is reached,substantially as described. 7

10. A centrifugal switch having; in combination, a rotary support, amovable contact member mounted upon said support, independent meansoperated by centrifugal force for moving the contact member, said meansbeing arranged to be held stationary until a certain predetermined speedof rotation is reached and then to be moved suddenly by an unbalancedcentrifugal force to deliver a blow upon the contact member,substantially as described.

11. A centrifugal switch having, in combination, a rotary support, amovable contact member mounted upon said support, and a weighted armpivotally mounted upon said support and articulated with said contactmember to actuate it when the support attains a predetermined speed ofrotation, substantial y as described.

12. A centrifugal switch having, in combination, a rotary support, acontact carrys ing lever mounted upon said support, a weighted armpivotally mounted upon said support, and a spring connecting the leverand arm acting to exert a ull in the direction to oppose the centrlfugalforce imparted to the wei hted' arm by the rotation of the support sustantially as'described.

13. A centrifugal switch having, in combination, a rotary support, acontact carrying lever mounted u on said support, a weighted arm pivotaly mounted on said support, a spring connecting the lever and arm andacting to exert a pull on the lever in the direction to maintain thecontact member in closed position, and means for limiting the outwardmovement of said arm.

In testimony whereof I aflix my signature,

in presence of two witnesses.

CLARENCE B. HANRIGHT.

Witnesses:

I HERBERT A. BALCOME,

CARLTON L. KENNEDY.

